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-   -   OEM Parking Brake Lever Study (http://www.jeepforum.com/forum/f96/oem-parking-brake-lever-study-1061720/)

ronjenx 07-01-2010 06:04 PM

OEM Parking Brake Lever Study
 
I have been wondering how the parking brake lever works.
People have had it fail, and it was not clear to me what failed.
This is how it works:

1. Here is an overview of the passenger side of the parking brake lever assembly.
The pin which loops over the black lever is installed to keep the tension spring from unwinding. It is removed after the cables are connected.
http://i776.photobucket.com/albums/y.../1Overview.jpg




2. Here is an overview of the driver's side of the parking brake lever assembly.
http://i776.photobucket.com/albums/y.../2Overview.jpg




3. A more detailed view of the various parts.
The tension spring is attached to the cable drum.
It keeps about 20 pounds pull on the cable when the parking brake is released. This removes the slack from the system.
The cable drum is made from two pieces, with one piece extending under the clutch spring.
The clutch spring is wound around the drum tightly enough to be a friction fit on the drum.
One end of the clutch spring extends from the bottom of the spring, and is anchored to the parking brake lever.
Lifting the lever causes the clutch spring to wind even more tightly around the drum, so the drum rotates with the lever, which pulls on the brake cable.
http://i776.photobucket.com/albums/y...lofSprings.jpg





4. As the lever is pulled up, the clutch spring, being anchored to the lever, rotates, tightening itself on the drum.
This drags the drum around with it, pulling the cable.
The clutch spring tail moves away from the stop, which is actually the thing that allows the clutch spring to wind itself tighter on the drum.
http://i776.photobucket.com/albums/y...utchSpring.jpg





5. Here the lever has been raised as if to apply the parking brake.
The spring clutch tail has also rotated away from the stop.
If you were to pull on the tail, toward the camera, it would unwind the clutch spring, making its diameter bigger, thereby releasing the cable drum. The lever position would not change, though. It would move freely as long as you followed the rotation with the spring tail.
When the lever is returned to the down position, the clutch spring tail also rotates toward the stop. It hits the stop just before the lever bottoms out. This releases the clutch spring, and the tension spring is free to rotate the cable drum, maintaining 20 pounds tension on the cable.
http://i776.photobucket.com/albums/y...x/5LeverUp.jpg





6. Here you see what breaks when you go to apply the parking brake, and hear a loud SNAP!
The lever will then be free to move, and no torque will be applied to the cable drum.
http://i776.photobucket.com/albums/y...hSpringArm.jpg

An ineffective parking brake could be caused by any one of several things:
Worn shoes
Shoes out of adjustment
Broken cable(s)
Broken clutch spring arm
Slipping clutch spring
Broken tension spring

JLC08JK 07-01-2010 08:09 PM

Whatever happened to just a lever with a cable attached?:dunno:
Thanks for the insight :thumbsup:
This will more than likely be helpful in the future :tea:

plac 07-01-2010 08:47 PM

you dog..

JeepScout3 07-01-2010 09:37 PM

Very informative. Not sure if I will need to know this, but having this knowledge, like anything else, could come in handy one day. Thanks for a solid overview.

djkbooth 08-08-2010 03:29 PM

Bump!!

Good info for others!!!

duramax58 09-15-2010 10:10 AM

e-brake assembly
 
thanks great photos BIG help jim

tennistom1 09-15-2010 11:04 AM

Great write-up and pics, Ronjenx. This Rube Goldbergian contraption, was no doubt a by-product, of the short-term marriage between Daimler & Chrysler. As with most Mercedes products, over-engineered in my opinion. I'm sure next time I'm on the Autobahn, the tow-truck driver, will have the spare part on top of his dash and it will be a snap for him to r/r. Probably does not lend itself well to trail fixes, glad I just bought a set of folding wheel-chocks. I will pull more gingerly from now on.

Thanks!

ronjenx 09-15-2010 11:46 AM

Quote:

Originally Posted by tennistom1 (Post 10128932)
Great write-up and pics, Ronjenx. This Rube Goldbergian contraption, was no doubt a by-product, of the short-term marriage between Daimler & Chrysler. As with most Mercedes products, over-engineered in my opinion. I'm sure next time I'm on the Autobahn, the tow-truck driver, will have the spare part on top of his dash and it will be a snap for him to r/r. Probably does not lend itself well to trail fixes, glad I just bought a set of folding wheel-chocks. I will pull more gingerly from now on.

Thanks!

Thanks!

I believe the design is an attempt at making the lever self-adjusting.
The lever gets a fresh grab on the drum each time it is released.
It's unfortunate the clutch spring arm, where it is anchored to the lever, is a weak point.

mrbodywork 09-15-2010 08:52 PM

I believe I was reading in the manual of my 2009 Rubicon that the E-brake is NOT self adjusting.

I need to tighten the cable because it has stretched and I'm looking for info on how to do the work myself.

Anyone else had this issue?

Bill

plac 09-15-2010 09:02 PM

Quote:

Originally Posted by mrbodywork (Post 10132449)
I believe I was reading in the manual of my 2009 Rubicon that the E-brake is NOT self adjusting.

correct. it is not self adjusting. there is no lever that moves the star adjuster. you have to open it up, remove the caliper so you can get to the adjustment hole in the back plate. if you go that far, its just as easy to remove the rotor and adjust the star easily. then get it tight enough so the rotor just has a tiny resistance when turning it.

ronjenx 09-15-2010 09:09 PM

Quote:

Originally Posted by mrbodywork (Post 10132449)
I believe I was reading in the manual of my 2009 Rubicon that the E-brake is NOT self adjusting.

I need to tighten the cable because it has stretched and I'm looking for info on how to do the work myself.

Anyone else had this issue?

Bill

The lever is self adjusting, because it gets a new grip on the cable drum each time it is released. The tension spring keeps about 20 lbs tension on the cable after the lever is released, to make up for some cable stretch. The tension spring won't make up for the need to adjust the shoes. Therefore, the brake shoes are not self adjusting.

Applying the parking brake in reverse, and forward, a few time can equalize the left and right sides, making the brake more effective.
Using this procedure, mine went from 5 clicks to hold the Jeep, to 3 clicks to hold the Jeep. That saved me from adjusting the shoes, this time.

This will not work if the lever goes much past 5 or 6 clicks to hold the Jeep.

The shoes can be adjusted without removing the wheel/tire/drum. but it's much easier if you do.

McKBrew 09-15-2010 09:14 PM

Another great post. You are the king when it comes to taking things apart.

M-Godzwon 01-17-2011 08:46 AM

The wife just snapped her brake last Friday. Thanks for this excellent post. I was about to climb under the Jeep and start there inspecting cables, but now you've saved me from getting 40 lbs of slush, sand, and salt all over myself.

1222 01-17-2011 09:00 AM

Quote:

Originally Posted by McKBrew (Post 10132582)
Another great post. You are the king when it comes to taking things apart.

Iíll second that.:thumbsup:
:cheers2:

ccsaunders 02-16-2011 07:03 PM

I've just finished the parking brake replacement and adjustment. My brake needed to be pulled up all the way and then the ferule on the cable that connects around the pulley on the brake lever snapped. I ordered a new parking brake model 52059887AB. I was able to install it without removing the entire center console. I removed just the storage compartment and was able to use a couple different length ratchets and extensions to remove the old and install the new one without too much trouble. Adjusting the brakes was worse than I'd hoped but still wasn't that bad. I do not believe there is anyway to adjust the star without pulling off the wheel and brake. My brake spoon just couldn't make contact and still have room to rotate the star. I pulled off the rotors so I could see how much (and whether) I was moving the star. The wheel don't spin very easily before adjusting the brake but I turned the star until the wheel noticeably dragged and then backed it off. (This meant I had to put the rotor back on to test.) When I pull the handle I get about 6 clicks until it is good and tight. Could it be tighter? Probably, but it's been so bad for so long I'll take what I can get. Thank you to all the people who've posted information on this topic. You saved me a couple hundred bucks.


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